Azilsartan medoxomil potassium is chemically described as (5-methyl-2-oxo-1,3-dioxo-4-yl)methyl-2-ethoxy-1-1{[2′-(5-oxo-4,5-dihydro-1,2,4-oxadiazol-3-yl) biphenyl-4yl]methyl}-1H-benzimidazole-7-carboxylate monopotassium salt of Formula I.

Azilsartan medoxomil potassium is a prodrug of Azilsartan of Formula II.

Azilsartan medoxomil potassium is an angiotensin II receptor blocker sold under the trade name EDARBI in USA and is indicated for the treatment of hypertension to lower blood pressure in the recommended dose of 40 mg taken once daily and escalation to 80 mg per day as necessary.
Azilsartan medoxomil potassium was described for the first time in U.S. Pat. No. 7,157,584 where its preparation and crystallization from acetone is presented, obtaining off-white crystal, having a melting point of 196° C.
U.S. Patent Application No. 20140113942 discloses process for preparation of Azilsartan medoxomil potassium Form I′, the process comprising: (a) dissolving purified Azilsartan medoxomil methylene dichloride solvate in one or more of suitable organic solvent to obtain solution of solvate; (b) adding potassium source solution to the solution of solvate to obtain Azilsartan medoxomil potassium in reaction mixture; and (c) obtaining Azilsartan medoxomil potassium by removal of solvent from the reaction mixture.
International (PCT) publication WO 2013/042067 discloses process for preparation of Azilsartan medoxomil potassium Form I by treating Azilsartan medoxomil with potassium source in the presence of at least one C4-9 ketone solvent such as methyl ethyl ketone, methyl isobutyl ketone, methyl isopropyl ketone, ethyl isopropyl ketone, butanone or acetophenone.
PCT publication WO2013/104342 discloses crystalline form of Azilsartan medoxomil potassium, wherein the crystalline form is form A, form B, form C, form D, form E, form F, form G, form H, form I, form J, form K or form L and wherein the crystalline form of Azilsartan medoxomil potassium is substantially pure.
International (PCT) publication WO 2013/124748 discloses novel crystalline forms of Azilsartan medoxomil potassium and process for its preparation. WO 2013/124748 also discloses process for the preparation of amorphous Form VI of Azilsartan medoxomil potassium by the use of an organic solvent wherein the said organic solvent is C1-C5 alcohol or mixture thereof.
International (PCT) publication WO2014/048404 discloses process for the preparation of Azilsartan medoxomil potassium of formula I, in which first a solvate of Azilsartan medoxomil with a solvent selected from the group that consists of dimethyl acetamide or N-methyl pyrrolidone or their mixtures with other solvents is prepared, the resulting solvate is optionally re-crystallized, and, in the next step, converted, without desolvating, into the potassium salt using a potassium source.
Azilsartan medoxomil potassium exists in different crystalline forms, which have significant differences from each other in appearances, solubilities, melting points, dissolution rates, bioavailabilities, stability, efficacy and the like. These properties impact the stability of the substance and in turn impact the stability of the formulation in which it is incorporated. It is always desirable to use substance which is more thermostable as it ensures more stable pharmaceutical formulation. Therefore, there is a need for novel crystalline forms of Azilsartan medoxomil potassium which are thermostable and have higher melting point as compared to the melting points of existing crystalline forms.